Because TNP claimed there would be no useful power from a PV setup for the entire winter in the UK.
It's quoted above, but I'll repeat it : "You need 6 months of batteries to tide you over the winter".
I thought I'd mention a real world counterexample.
My experience with a standalone solar system (not powering a house) is that you need about a weeks worth of capacity.
Met Office sunshine figures Northern England 1971 - 2000 *
The conclusion?
Size an array for demand during the worst month and it will probably overproduce by about 4.4 times in the best month
Reality is that it's about 5.5 times according to the calculations at
Real world monitoring of the solar output on this off grid system I briefly mentioned above very closely tracks the published met office figures for the geographical area which can obviously be above or below the long term average.
To meet 1kW of average demand then you need (24-1.3) = 22.7 hours of reserve capacity in December
Assume a maximum discharge level of 60% of peak capacity to keep battery life to 5 years. That means a battery capacity of 38 hours to meet December demand
But the sun might not shine for a few days, four 24 hour periods in a row without sun is a reasonable assumption but without going below that the imposed depth of discharge
That increases the battery capacity required to about 160 hours, or about 1 week, like I said earlier :)
1000W average load x 160 hours160,000 Wh of capacity
Or, at say 48v nominal, 3300Ah cells
It's around 1000 quid for a 4v 1600Ah cell, so that is 24 cells or
24000 quid1000W load 24 hours a day for 31 days is 744kWh
To supply 744kWh during December needs about 11kW of solar pv in the north of the UK
(Using
Two 6kW systems on Ebay are 15k (because I can't be arsed to find a more accurate figure)
Solar array lasts for 25 years, five battery replacements during that time.
Total cost of ownership
5 x 24000 for the batteries + 15000 for the panels = 135kAll that to supply 1kW average load for 25 years
25 years x 365 days x 24 hours = 219,000 hoursat 1kW load, that is 219,000KWh
Cost of that electricity
61 p / kWhIn the situation I mentioned at the top of this posting the load is far lower and there is zero possibility of a grid connection, and if one were to be provided the cost would be in the order of many hundreds of thousands of pounds. A fossil fuelled generator is not permissible due to noise considerations, nor is a wind turbine for reasons that can't be specified here.
The solution when offgrid, is to be frugal and only use power when you really need to.
If you're using solar pv, its so expensive per unit that the first question is always what loads can be shedded, by making non-electric or going without. Kettle and cooker would be gas, fridge could be gas, and an electric dryer makes little sense on grid, and none off.
NT
They certainly used to
Jonathan
We have photo voltaic panels and solar tubes for hot water. So far as I can tell from my meter monitoring, the solar photo voltaic generates about the same amount nof electricity that the pump for the hot water system uses. So the timing is perfect.
Jonathan
Is there not a wood burning stirling engine thing that makes electric? (The gas one was on that homes of the future thing)
He can still get a "FIT" payment for it so he may consider it an investment. Though there is no FI obviously..
They certainly used to
They have/had wind turbines too. But not everyone has a suitable site.
They virtually stop working in rain and when covered in snow.
More like 100:1 I can tell you from first hand experience. Not including snow effects.
May as well just turn the immersion heater on when it's sunny.
Polar air effect. They are much more efficient in the cold and atmospheric moisture is low, a big help. Also 24 hour sunshine in Summer (and nilin Winter)
he
Well in the Winter quarter, my PV panel generates a quarter of the electricity it does in the Summer quarter. But there are plenty of Winter days when it does very little. December is the worst month as you might expect.
A true real world example, not BS from TurNiP Dunno why he rabbits on about stuff he has zero knowledge of.
Well, you'll get some power I suppose, for 6 hours a day. But nothing serious.
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Met office statistics are not very helpful. Your calculation falls down on the point that there is sunshine and sunshine. A slight haze can knock 15%-20% off the generating capacity. A passing cloud can knock off 75% of capacity. You need to work off actual figures. Local sunrise/sunset has an effect. Orographic and microclimates.
You need to work off an insolation map and even they are very poor.
Not quite.
What I was pointing out was that the summer to winter variation of output is approximately 10:1.
That leads to two strategies
1/. Buy enough panels so that the 10% of summer output you get in winter is enough for winter needs (which are always far higher) and simply waste the excess in summer when you don't need it.2/. Arrange to store summer electricity for the winter, in which case you need about half a million quids worth of batteries per house, with a lifetime of only 5-7 years.
That or 10 times as big a panel when you only need batteries to tide you over a dull week instead.
No, you are falling into the classic mistake of sloppy thinking.
You believe that the word 'could' has a single meaning regardless of context, so that the statement 'I could catch the 10:37 train to London' has the same essential truth value as 'I could go on a rocket to the moon'
I too hae a motorhome of advancing age and modest dimension. It too could hae all its meagre electrical needs met by a very large solar panel, even in winter. Of course it has a gas fire, and a gas cooker and a gas fridge, only 8 lights - of which I dare only use a single fluorescent or the battery is flat in two days..and that's in summer.
But if that's living, yes I COULD get all the electricity I used from sunlight.
As long as I have enough gas.
I published the insolation figures from a solar panel lobby. Who would be expected in anything to overstate the case. They don't as it happens. December insolation is 10 times less than July. So its up to readres to say whether you are lying, or they are.
I note you are still connected to the grid.
the way PV is paid for, you will still make money if 80% of your electricity comes from it.
>
thats averaged over a MONTH so you still need enough battery capacity to cover that month.
I take around 1Kw. Big house, needs a lot of lighting.
Others use much more.
And hope you don't get more than 160 sunless hours. Or that your winter electricity demand is average, when in fact its generally higher as you spend more time indoors with the lights on and the telly on.
Bad assumptions. Add in the cost of capital as the power companies do, and the cost of maintenance at around 15% of capital cost (in total O&M
so every year add on £20.25k O&M and interest
Going on the 1Kw average draw, over that year, that adds another £2.31 per unit
Bringing the total cost of the electricity up to almost exactly £3 a unit.
Whereas coughing up 50 grand to get connected over a 25 year period where someone ELSE does all the maintenance,adds 2 grand a year to the price of the total electricity bill - a mere snip at 22p plus the notional electricity cost of 10p - a grand total of 33p before interest, and we will put that on at 7.5% ..adding a further 42p to the cost per unit.
So.
To get connected: 75p a unit over 25 years
DIY approach: £3 a unit. And no guarantee of reliable large winter power.
And which house will have more resale value? The one that comes with a high maintenance bill, a set of solar panels on their last legs, and a lot of scary electronics and a frankly dangerously explosive battery pack in the cellar, or one that comes 'with mains electricity'
And have a lot of bottled gas.
>
:-)
Gas if gas available.
My point was comparing =A360,000 spend re...
- Grid connection spending =A360,000.
- Running red diesel generator for peak loads, running sufficient PV & batteries for background loads (fridge, lighting, tv, laptop) spending =A360,000 over N years (ie, how long would it last, including interest of 4%/yr re typical gov't bond funds).
The answers thus far seem to be "PV for off grid". That is a "non-starter" unless you live on sandwiches, have TV, simple lights, mobile phone & laptop and that is it, a small mini fridge, an awful lot of insulation & live in one room. I believe even the Arctic science bases only use PV for "critical sundries" with the rest via diesel generators and heaters. PV is ideal for radios & communication, TV and emergency lighting, emergency potable water pumps.
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